I came here to post a problem on exactly this! Running on an intel haswell laptop so it doesn't surprise me other intel video driver users are seeing this.. I'm on Firefox 24 with the SNA option enabled for the intel video driver. Toggling hardware acceleration in flash doesn't seem to matter (same goes for editing the mms.cfg file in /etc/adobe, no effect.)

Issues only seem to occur on certain sites. Aggressive content filtering seems to have some role but doesn't explain everything.

Examples:

youtube works fine. Even full-screen.
speedtest.net's plugin shows up if I suspend content filtering. It looks fine, but if I scroll the flash embed off-screen even partially the image is all corrupted.
veoh's site is completely unusable. (Screenshot: http://img198.imageshack.us/img198/108/g85.png)

Other random flash embeds exhibit unusual flickering when the mouse moves over it. Sometimes the content can be seen but often it is outright corrupted; it does not appear to be random. The corrupted display looks like it's a garbled mess of what is supposed to be actually drawn to the screen. The colours and patterns within the nonsense are not arbitrary that's for sure. Either flash is broken or the intel driver is not working right with something. EDIT: I have click-to-play enabled on firefox. It's never been an issue on my other computers though.

Flash is 11.2.202.310 here with +64bit +sse2 flags.

I have an old laptop with nvidia drivers and I have never seen this issue with Flash which further suggests intel drivers have a role in this problem._________________ProtonMail - Free encrypted e-mail from Switzerland
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Incidentally, the firefox24 that worked fine for me on fglrx/RadeonHD 5770, I was forced to move the install to a Intel HD3000 graphics machine, and it retains its good working state._________________Intel Core i7 2700K@ 4.1GHz/HD3000 graphics/8GB DDR3/180GB SSDWhat am I supposed watching?

All flash ads, youtube content and the like viewed in Firefox are colour negative, and compressed horizontally into half the frame provided. In addition, the static ads flicker and flash annoyingly.

I tried changing over to gnash instead of adobe flash, but this had no effect on the problem.

In Opera, I see subtly different effects, mainly colour countouring in a wide range of garish colours.

To me the most mystifying part of this is that, if I download a .flv movie, which I assume to be flash, it plays perfectly in adobe or gnash. It seems that use within a browser is needed to show the effects.

For all those with flash issues in firefox, you can -system-cairo and emerge firefox and be fine. We know it is a cairo issue when using system-cairo but have not raced the actual problem to component in cairo that is causing bug.

For all those with flash issues in firefox, you can -system-cairo and emerge firefox and be fine. We know it is a cairo issue when using system-cairo but have not raced the actual problem to component in cairo that is causing bug.

Thanks Lebkoungcity, I struggled for days to find the solution to my adobe-flash garbled graphics after moving to systemd. In the event that it might help others with a similar system and problem, I mention that I am running a slave mythfrontend and webbrowser on an optiplex 32bit dual intel processor machine, with intel (i915) graphics. I found the article you mentioned very useful, and it seems to confirm that the problem lies with the intel graphics driver.